Perhaps there could be conflict if the adjacent key is resonating into the wrong tube as it overlaps the key's territory but I think I've got this solved by staggering the sharps so their nodal point (peg) coincides with the center of the adjacent key. This won't be true for directly adjacent naturals. Possibly those conditions could be fixed by blocking the opening parallel to the adjacent key. That would be like the small hole in a guitar using the larger resonator of the guitar body? I suspect it won't matter too much. Looking at school alto xylophones in a single shared resonator box, they taper the bottom of the box a bit but it's all open to all the keys and not very precise.